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Larson said blight shuts down the photosynthetic capacity of plants. That, in turn, causes yield losses because the kernels don't fill out to full potential. “We're seeing significant yield losses in some fields — as much as 30 percent (40 to 50 bushels per acre).”

To the west, Arkansas corn has its own problem — rust. “I'm in Lee County (in east Arkansas) looking at corn fields,” says Jason Kelley, Extension corn specialist. “Corn here, as well as in the rest of the state, is showing the results of rust. Leaves are desiccated.

“I just came out of a field of hybrids that don't have much resistance. The rust was all the way to the plant tops. The plants dried down a lot quicker than they should have. I'm seeing the same thing all over the state.”

Kelley says that when kernels were mostly filled, rust robbed the plants of their “greenness.” The plants had to cannibalize their own stalks to finish filling out the grain. “Very, very weak stalks” resulted.

“From the road, the crop looks fine,” says Kelley. “Out in the field, though, you can see there's a real issue. You can barely push on a stalk, and it falls over. A storm of any kind — especially a wind storm — will put a lot of our corn on the ground.”

Mississippi is seeing much the same due to blight. “Stalks are very weak, and lodging could occur if a storm blows through,” says Larson. “Fear of that will lead some of farmers to harvest between 20 percent and 25 percent moisture. Some fields were harvested as early as July 20.”

The worst blight-affected fields in Mississippi are where corn followed corn, because the blights overwinter on corn residue or trash.

However, Larson also sees severe infections in first-year corn fields with susceptible hybrids. That's particularly true in hot spot areas with a history of large corn acreage — Noxubee County, Hollandale, Glendora, some areas of Yazoo County and around Vicksburg.

“Most moisture levels are in the lower 20s to around 30 percent,” says Larson. “We're probably around 10 percent harvested. We're just getting started in the Delta and haven't made a lot of progress in east Mississippi.”

With warmer weather and less rain, Louisiana's corn is beginning to “dry down,” says David Lanclos, Extension corn specialist. While the crop has experienced more problems than is usual, Lanclos remains “relatively optimistic about yield potential. I do not think we will lose much more than 10 percent to 15 percent.”

Lanclos says Louisiana's latest problems include “morningglories and rotting of some portions of ears. Because of rain, some husks have been loosened to the point where moisture on the end of the ear rotted kernels.”

The several inches of lost ear can add up very quickly, he says. “The worst part is there's nothing we can do about it.”

In Arkansas, Kelley says rust normally comes into the state's crop after grain is filled and doesn't make much of an impact. “This year, the disease came in a little earlier — although not early enough to stop grain-filling. Weather conditions were right for rust, and there's plenty of corn in neighboring states. Wind picks up diseases there and blows them to us.”

There's nothing that can be done to remedy the situation, says Kelley. Producers need to harvest affected fields as early as they can.

“They may need to harvest at a slightly high moisture level — hopefully, they've got a grain dryer. Otherwise, it's a choice between dockage and risking a storm blowing over the crop. We should begin harvest in earnest soon (during the second week of August). Some combines are running here and there, but I haven't seen a harvested field yet.”

Early harvest in Arkansas is positive, says Kelley. “Some large dryland field-scale plots in central Arkansas yielded 175 bushels per acre. That's wonderful news. I'm also getting reports from around Eudora (on the Arkansas/Louisiana border). They're cutting around 160 bushels — down 20 bushels compared to last year. We're not happy about the drop in yield, but it wasn't unexpected. Overall, this a good start for us.”

In Tennessee also, corn has had more widespread rust problems than normal. “In the past, we saw rust in isolated areas,” says Angela Thompson, Extension corn specialist. “I'm not as concerned about corn planted in March and early April. Those crops were well into black layer when the rust hit. I'm far more worried about later-planted corn.”

Still, says Thompson, Tennessee's yield potential is good — especially for the earlier crop. “I haven't heard of anyone harvesting, but we're very close — especially in the southwest corner of the state,” she says.

Regarding rust, Kelley says there are “definite differences” among hybrids. Some plants have rust all the way to the top — the whole plant is “just inundated. In other hybrids, rust isn't nearly that bad.

“I don't think rust will hurt yield too badly. Test weights in the worst fields may be a little lighter than usual, but barring a windstorm, we're expecting a good harvest. Our state record is 145 bushels per acre. We should be around 140 bushels.”